Heat Adaptation in Military Personnel: Mitigating Risk, Maximizing Performance

Abstract

The study of heat adaptation in military personnel offers generalizable insights into a variety of sporting, recreational and occupational populations. Conversely, certain characteristics of military employment have few parallels in civilian life, such as the imperative to achieve mission objectives during deployed operations, the opportunity to undergo training and selection for elite units or the requirement to fulfill essential duties under prolonged thermal stress. In such settings, achieving peak individual performance can be critical to organizational success. Short-notice deployment to a hot operational or training environment, exposure to high intensity exercise and undertaking ceremonial duties during extreme weather may challenge the ability to protect personnel from excessive thermal strain, especially where heat adaptation is incomplete. Graded and progressive acclimatization can reduce morbidity substantially and impact on mortality rates, yet individual variation in adaptation has the potential to undermine empirical approaches. Incapacity under heat stress can present the military with medical, occupational and logistic challenges requiring dynamic risk stratification during initial and subsequent heat stress. Using data from large studies of military personnel observing traditional and more contemporary acclimatization practices, this review article (1) characterizes the physical challenges that military training and deployed operations present (2) considers how heat adaptation has been used to augment military performance under thermal stress and (3) identifies potential solutions to optimize the risk-performance paradigm, including those with broader relevance to other populations exposed to heat stress.

Epidemiology of Exertional Heat Illness in the Military: A Systematic Review of Observational Studies

“…These units may be required to kill enemy forces and are trained to engage in dismounted ground close combat (DGCC), among other physically arduous functions. There are multifactorial reasons for the increased risk of EHI among individuals in these high-risk groups [ 17 ]. Apart from the physically arduous functions that increase internal heat production, these individuals may need to be rapidly deployed, risking inadequate time for acclimatisation before action, which may delay heat adaptation and increase the risk of EHI [ 17 ].…”

“…During exercise in the heat, the mechanism of heat loss is via cutaneous vasodilation and evaporation of sweat [ 15 ]. As core temperature rises with continuous exertion and metabolic heat production, the physiological cooling mechanism of heat loss through evaporation of sweat may impeded by the protective clothing increasing the risk of EHI [ 16 , 17 ]. Furthermore, evidence suggests that high levels of motivation to push through the heat strain and beyond physiological limits without self-pacing also increases the risk of EHI [ 3 , 18 ].…”

“…This may include training allied forces, insurgency work or counter terrorism, and full-scale war. Therefore, the occurrence of EHI in military service members is a threat to any military operation given that most cases of EHI are incapacitated and accounts for significant morbidity [ 8 , 17 ]. A study by Cox et al revealed that at a field hospital in Camp Bastion, 1131 military admissions were reported for a total of 1368 medical patients (both civilian and military) between 2011 and 2013 [ 19 ].…”

Echocardiographic changes following active heat acclimation

“…TTE is a useful tool to demonstrate and quantify cardiac adaptation. This has several implications to utilise TTE as a research tool in elite athletes ( Périard et al, 2016 ; Tyler et al, 2016 ) firefighters, miners, the military or aid workers ( Parsons et al, 2019 ) particularly in the development of tailored rapid HA regimes. Echocardiography in heat acclimation merits further study.…”

Sex, gender or occupational psychology: what matters most to preventing heat-related illnesses and improving outcomes for women in ground close combat?

“…In evaluating the potential impact of these differences on the deployment to hot environments of GCC troops, which may now include female SP, the authors rightly alluded to the dual military objectives of maximising performance while minimising risk of heat illness. 3…”